Retransmission Based Beamforming

This application is the United States national phase of International Patent Application No. PCT/EP2022/059094 filed Apr. 6, 2022, the disclosure of which is hereby incorporated by reference in its entirety.

The present disclosure relates to a method and device for retransmission of data in wireless communication.

Wireless communication has been advancing over several decades now. Exemplary notable standards organizations comprise the 3rd Generation Partnership Project (3GPP) and IEEE 802.11, commonly referred to as Wi-Fi.

In any wireless communication, the transmission of data may fail due to various reasons.

Retransmission is an effective way to improve performance of wireless communication systems, wherein packet retransmission is often requested when an error is determined in the received packet. For instance, an automatic retransmission request (ARQ) may ensure a low packet error rate.

The efficiency of ARQ may be improved by reusing the data from the previous (re) transmissions instead of discarding them. This technique, termed the hybrid ARQ (HARQ), includes the Chase Combining (CC) and Incremental Redundancy (IR). HARQ is supported in the LTE system for reliable data transmission together with Multiple Input Multiple Output (MIMO).

However, when the reception quality of a signal deteriorates, this may affect a retransmission alike.

The motivation of this disclosure is to provide robustness for communication links.

Methods and devices are described herein for wireless communication implementing a beamforming-based retransmission strategy that may enhance system performance.

According to an embodiment, a communication device is provided for wireless communication with another communication device, comprising: a transceiver section configured to transmit data to the other communication device using a first beam; and processing circuitry configured to determine whether the line of sight path to the other communication device is blocked, wherein the transceiver section is further configured to retransmit the data using a second beam, wherein when no blockage of the line of sight path is detected, the beamwidth of the second beam is set to a first width; and when a blockage of the line of sight path is detected, the beamwidth is set to a second width, wherein the second width is larger than the first width.

According to further embodiments, apparatuses are provided for transmission and reception of the signals which comprise processing circuitry configured to perform the steps of the respective transmitting and receiving methods, as well as a transceiver configured to receive or transmit the signals.

The above-mentioned circuitry may be any circuitry such as processing circuitry comprising one or more processors and/or other circuitry elements.

These and other features and characteristics of the presently disclosed subject matter, as well as the methods of operation and functions of the related elements of structures and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the disclosed subject matter. As used in the specification and the claims, the singular form of “a,” “an,” and “the” comprise plural referents unless the context clearly dictates otherwise.

For purposes of the description hereinafter, the terms “end,” “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” “lateral,” “longitudinal,” and derivatives thereof shall relate to the disclosed subject matter as it is oriented in the drawing figures. However, it is to be understood that the disclosed subject matter may assume various alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments or aspects of the disclosed subject matter. Hence, specific dimensions and other physical characteristics related to the embodiments or aspects disclosed herein are not to be considered as limiting unless otherwise indicated.

No aspect, component, element, structure, act, step, function, instruction, and/or the like used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to comprise one or more items and may be used interchangeably with “one or more” and “at least one.” Furthermore, as used herein, the term “set” is intended to comprise one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and/or the like) and may be used interchangeably with “one or more” or “at least one.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based at least partially on” unless explicitly stated otherwise.

illustrates an exemplary communication system CS in which Tx represents a transmitter and Rx represents a receiver. The transmitter Tx is capable of transmitting a signal to the receiver Rx over an interface IF. The interface may be, for instance, a wireless interface. The interface may be specified by means of resources, which can be used for the transmission and reception by the transmitter Tx and the receiver Rx. Such resources may be defined in one or more (or all) of the time domain, frequency domain, code domain, and/or space domain. It is noted that in general, the “transmitter” and “receiver” may be also both integrated in the same device. In other words, the devices Tx and Rx inmay respectively also comprise the functionality of the Rx and Tx.

The present disclosure is not limited to any particular transmitter Tx, receiver Rx and/or interface IF implementation. However, it may be applied readily to some existing communication systems as well as to the extensions of such systems, or to new communication systems. Exemplary existing communication systems may be, for instance the 5G New Radio (NR) in its current or future releases, and/or the IEEE 802.11 based systems such as the recently studied IEEE 802.11be or the like.

IEEE 802.11, commonly referred to as Wi-Fi, has been around for three decades and has become arguably one of the most popular wireless communication standards with billions of devices supporting more than half of the worldwide wireless traffic. The increasing user demands in terms of throughput, capacity, latency, spectrum and power efficiency calls for updates or amendments to the standard to keep up with them. As such, Wi-Fi generally has a new amendment after every 5 years with its own characteristic features. In the earlier generations, the focus was primarily higher data rates, but with ever increasing density of devices, area efficiency has become a concern for Wi-Fi networks. Due to this issue, the last (802.11ax) and upcoming (802.11be) amendments have focused more on the efficiency issue.

illustrates a transmitting deviceaccording to some exemplary embodiments. The transmitting devicemay be a part of any wireless communication device such as STA or AP, or, in general base station or terminal. The transmitting devicecomprises memory, processing circuitry, and a wireless transceiver(or a wireless transmitter), which may be capable of communicating with each other via a bus. The transmitting devicemay further comprise a user interface. However, for some applications, the user interfaceis not necessary (for instance some devices for machine-to-machine communications or the like).

The memorymay store a plurality of firmware and/or software modules, which implement some embodiments of the present disclosure. The memorymay be read from by the processing circuitry. Thereby, the processing circuitry may be configured to carry out the firmware/software implementing the embodiments. The processing circuitrymay comprise one or more processors, which, in operation, may perform the method steps shown inor. The wireless transceiver, in operation, transmits the generated transmission signal.

Retransmission may be an effective way to improve performance of wireless communication systems, wherein packet retransmission is often requested when an error is determined in the received packet. An automatic retransmission request (ARQ) may ensure an extremely low packet error rate.

The efficiency of ARQ may be improved by reusing the data from the previous (re) transmissions instead of discarding them. This technique, termed the hybrid ARQ (HARQ), comprises the Chase Combining (CC) and Incremental Redundancy (IR). HARQ is supported in the LTE system for reliable data transmission together with Multiple Input Multiple Output (MIMO).

Combined with HARQ, MIMO may potentially provide higher throughput packet data services with higher reliability. MIMO equipped with a high number of antennas at the base station can communicate with multiple users simultaneously. Since the number of antennas is limited in a massive MIMO base station, if the number of users becomes more than the number of antennas, a proper user scheduling scheme may be applied before precoding to achieve a higher throughput and sum-rate performance.

Next-generation cellular communication systems, or 5G, will be assisted by technologies that produce significant improvements in cell throughput. In recent years, various studies have focused on massive MIMO systems, which are considered to play a significant role in 5G. Massive MIMO systems are MIMO systems wherein the precoders and/or detectors contain numerous antennas. Such large number of antennas enable higher spectral efficiency and energy efficiency.

Several types of antennas can be used for this purpose, one of which is called a smart antenna. Smart antennas are organizations of numerous antenna elements at BSs and mobile stations of wireless communication links, in which signals are appropriately managed, to improve the wireless mobile link and increase the performance of the system.

Beamforming is the application of multiple radiating elements transmitting the same signal at an identical wavelength and a fixed phase, which combine to create a single antenna with a longer, more targeted stream that is formed by reinforcing the waves in a specific direction.

In wireless communication systems, transmit and receive beamforming is used for signal transmission from BSs with multiple antennas to one or multiple pieces of user equipment that should be covered. The objective of transmit beamforming is to maximize each user's received signal power while minimizing the interference signal power from the other users, hence increasing capacity. This can be achieved by transmitting the same signal from all transmitters with different amplitudes and phases. These multiple versions of the transmitted signal will pass through different MIMO channels such that they are added constructively at the desired users and destructively at other users.

The successful operation of MIMO systems requires the implementation of powerful digital signal processors and may make use of an environment with lots of signal interference, or “spatial diversity”; that is a rich diversity of signal paths between the transmitter and the receiver.

The diversity of arrival times, as the signal is reflected from different obstacles, forms multiple paths that can deliver path redundancy for duplicate signals or increase the channel reliability by transmitting different parts of the modulated data.

As mentioned above, beamforming is the application of multiple radiating elements transmitting the same signal at an identical wavelength and a fixed phase, which combine to create a single antenna with a longer, more targeted stream that is formed by reinforcing the waves in a specific direction.

The more radiating elements make up the antenna, the narrower the beam can be. An artifact of beamforming is side lobes being radiated in other directions than the main lobe. The more radiating elements that make up the antenna, the more focused the main beam is and the weaker the side lobes are. While digital beamforming at the baseband processor is mostly used today, analog beamforming in the RF domain may provide antenna gains that mitigate the lossy nature of 5G millimeter waves.

Meanwhile, array processing, such as beamforming is playing a role in fulfilling the increased demands of various communication services. The beamforming technique is based on the antenna array with a small inter-element distance, and it can cancel or coherently combine the multipath components of the desired signal and restrain interfering signals that have different directions. For instance, beamforming has been implemented in the Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system.

Beamforming is already supported for Time Division Duplex (TDD) mode of recent 3GPP systems (e.g. NR TDD, LTE TDD) thanks to the channel reciprocity; however, only a single antenna port is available for transmitting one stream of data. For example, in LTE-Advanced system, enhancement of beamforming which can support multi-stream transmission has been considered to further improve the system capacity.

Link adaptation, comprising adaptive coding and modulation (ACM) and others (such as Power Control), is a term used in wireless communications to denote the matching of the modulation, coding, and other signal and protocol parameters to the conditions on the radio link (e.g., the path loss, the interference due to signals coming from other transmitters, the sensitivity of the receiver, the available transmitter power margin, etc.). Diversity can be applied on both the receiver side (receives diversity) and the transmitter side (transmits diversity). When using diversity, the antennas may have a low mutual correlation, since diversity is a way of combating fading on the radio channel. For receive diversity, different types of combinations of received signals can be used, such as Maximum-Ratio Combining (MRC) and Interference Rejection Combination (IRC).

User relaying schemes may use jointly designed linear beamformers for different transmission phases for minimization of the transmission time required until both users have received their required amount of information. HARQ may be used as an adapting retransmission protocol.

However, when the reception quality of a signal deteriorates, this may affect a retransmission alike.

In some embodiments, optimizing the beam form may lead to concentrating energy towards a specific region by directional communication which eliminates multipath in the environment and poorly scatters the transmitted signals. Therefore, the communication is easily interrupted by any obstacle in the beam direction. The line of sight (LOS) path is prone to more signal attenuation in comparison to indirect paths or NLOS paths under blockage conditions.

In general, retransmission schemes may improve the throughput and reliability in wireless transmission. When a packet is not received without an error, the packet may be retransmitted and the receiving side can use the retransmitted packet and, optionally, the originally received version of the packet to decode the data comprised in the packet.

In transmission schemes involving multiple antennas either on one of or on both of the transmitting side and the receiving side, diversity and/or beamforming schemes may be used for both or one of the transmission of original packets and retransmitted packets.

The exemplary wireless communication system shown incomprises one base station (BS)that comprises multiple antennas. The BS may use beamforming to serve multiple users in the network. For simplicity purposes only,shows one userout of the multiple users. However, the BS may also serve two users or any number of users, for example with beams having different directionality and/or power. Furthermore, in this example the usermay have one antenna. Alternatively, the user may have multiple antennas.

In this example, the network uses time division duplexing (TDD) mode. From this, the channel reciprocity may be used as feedback between the user and the BS. In other words, in the TDD mode, uplink and downlink are time-multiplexed, so that in general uplink reception quality may be used to estimate downlink reception quality and vice versa.

In an exemplary state of the communication system, beam training may be completed before transmission of data. However, a retransmission of transmitted data may still become necessary if errors occur during the data transmission. This may be the case, for instance, because the beam is blocked. In the example shown in, the beam is directed towards the line-of-sight (LOS) between the BSand the UE. An object blocking this LOS may lead to a blockage of the beam.

The above-mentioned retransmission may be triggered according an (H) ARQ protocol. The present disclosure is not limited to any particular (H) ARQ protocol. For example, a retransmission may be requested by the user, e.g., by sending a negative acknowledgement or the like. Here, when referring to a user, what is meant is a user device, such as a UE or STA. Alternatively, the BS may have failed to receive an acknowledgement for data that was sent to the user (e.g., within a predetermined time and/or within other predetermined resources) and consequently, the BS may decide to retransmit the data. In other words, the retransmission of data may be performed upon explicit request of the receiving side or it can be triggered by determining that a positive acknowledgement has not been received as expected. As is known in the art, the receiving side (user) may determine whether the data have been received correctly, e.g., by applying an error detection approach such as checking the cyclic redundancy check (CRC) code attached to the data. The present disclosure is not limited to any particular determination whether the data have been received and/or whether the received data could be decoded correctly (with or without combining of different redundancy versions as in the HARQ approaches).

For example, the communication system shown inmay be an indoor communication system. However, the communication system may also be an outdoor communication system and may be for short range communication or long range communication or any kind of wireless network. In the millimeter-wave band, multipath reflection can be suppressed by using circular polarization and narrow-beamwidth receiving antennas. Therefore, indoor communication systems may use millimeter-wave to keep the direct connection between base stations and remote terminals.

Human bodies may block the propagation paths in the 60 GHz band (may also be related to as mm-wave) in the indoor environment. This may break mm-wave links. The mm-wave links may be vulnerable to blockage by the human body which is mainly comprised of water. Several kinds of blockages are possible and ways to detect blockage will be discussed later. For instance, received signal strength indicator (RSSI) variation may be used to detect a blockage on the mm-wave link during a time window. In some embodiments, an indication of blockage may be determined when the RSSI indicates low signal strength over a larger bandwidth. It is noticed that RSSI is only an exemplary measure for indicating signal quality or signal strength. Any alternative measure may be used as well. For example, Signal to Noise Ration (SNR), pathloss, or other parameters.

Antenna beamforming may play a key role in achieving robustness to LOS blockage. Measures adopted to counter LOS blockage may comprise beam steering towards non-line of sight (NLOS) links and/or the use of reflectors and/or relay-based schemes. Since the changes in the RSSI are changed based on TDD mode, this means that a blockage is happening in the system and could be due to, for instance, human blockage or object moving.

Examples for objective moving may comprise a relative movement between the transmitter and the receiver. Several methods may be used to measure this comprising a Doppler-based measurement and/or tracking approaches possibly using coarse-detection and/or fine-detection.

Attenuation of received signal strength (RSS) caused when a human blocks a LOS path, called human blockage, is an open issue in mm-Wave communications. Concentrating energy towards a specific region by directional communication eliminates multipath in the environment and poorly scatters the transmitted signals. Therefore, the communication may be easily interrupted by any obstacle in the antenna direction. As a common result of the prior art studies, the LOS path is prone to more signal attenuation in comparison to indirect paths or NLOS paths under blockage conditions.

A goal of the present disclosure may be providing robustness for communication links against blockage by exploiting the beam specification to do the retransmission. Based on the prior art, different kinds of blockage may exist as, for instance, human blockage impact and/or objective moving.

New retransmission strategies are proposed that are compatible with HARQ protocol-based mm-wave and that may increase the signal-to-noise ratio (SNR) by exploiting the beam properties, increasing the robustness of delay, and/or overcoming the blockage.